The invention relates generally to the heating of liquids, and specifically to those devices wherein rotating elements are employed to generate heat in the liquid passing through them.
Of the various configurations that have been tried in the past, types employing rotors or other rotating members are known, one being the Perkins liquid heating apparatus disclosed in U.S. Pat. No. 4,424,797. Perkins employs a rotating cylindrical rotor inside a static housing and where fluid entering at one end of the housing navigates through the annular clearance existing between the rotor and the housing to exit the housing at the opposite end. The fluid is arranged to navigate this annular clearance between static and non-static fluid boundary guiding surfaces, and Perkins relies principally on the shearing effect in the liquid, causing it to heat up.
An example of a frictional method for producing heat for warming a fluid is the Newman apparatus disclosed in U.S. Pat. No. 5,392,737. Newman employs conical friction surfaces in order to generate heat, the generated heat passing into a fluid reservoir surrounding the internal elements of the device, and where the friction surfaces are engaged together by a spring and adjustment in the compression of the spring controls the amount of frictional rubbing that takes place.
Such prior attempts at producing heat have suffered for a variety of reasons, for instance, poor performance during operation, and the requirement of complicated and expensive components. Scale build-up is another cost factor should subsequent tear down and refurbishment be then needed. Similarly, because friction materials eventually wear out, they must from time-to-time be replaced.
A modern day successor to Perkins is shown in U.S. Pat. No. 5,188,090 to James Griggs. Like Perkins, the Griggs machine employs a rotating cylindrical rotor inside a static housing and where fluid entering at one end of the housing navigates past the annular clearance existing between the rotor and the housing to exit the housing at the opposite end. The device of Griggs has been demonstrated to be an effective apparatus for the heating of water and is unusual in that it employs a number of surface irregularities on the cylindrical surface of the rotor. Such surface irregularities on the rotor seem to produce an effect quite different than the aforementioned fluid shearing of the Perkins machine, and which Griggs calls hydrodynamically induced cavitation. Also known as the phenomena of water hammer in pipes, the ability of being able to create harmless cavitation implosions inside a machine without causing the premature destruction of the machine is paramount. These surface irregularities in Griggs are in the form of radially drilled holes over the length of the cylindrical rotor. The Griggs machine has been shown to work well and is currently known to be used in a number of applications. However, the manufacture of the rotor takes a disproportionate amount of workshop time, due almost entirely due to the time taken to drill so many radial holes. Were it possible to have fewer holes in the rotor, a worthwhile advantage would be gained.
An important consideration, especially in Griggs, is the protection of bearings and seals against deterioration caused by high temperatures and pressures in the fluid entering and exiting the machine. In the case of Griggs, separate detachable bearing/seal units are deployed, externally attached to the main housing surrounding the rotor in order to space the bearing and seal members well away from the clearance surrounding the rotor. The requirement for such detachable bearing/seal units may increase expense and complication and there therefore is a need for a new solution whereby the effects of high temperatures and pressures are less harmful to such bearings and seals.
The present invention seeks to alleviate or overcome some or all of the above mentioned disadvantages of earlier machines, in a device that is relatively simple to implement, preferably with fewer component parts, and or requiring fewer machining operations. For certain applications, there may be advantage through the deployment of deeper holes in the rotor, as compared to the depth of holes taught by Griggs, for improved shock wave transmissions from the cavitation implosion zones to maximum power efficiency in performance. As well as by keeping complication to a minimum and avoiding expensive and time-consuming machining operations, there would be further advantage if the occurrence of the cavitational effect on the liquid through water hammer could be generated in openings that are cast in the rotor rather than machined conventionally, or whereby other changes can be incorporated in the rotor to compensate for having fewer holes.